A black councillor has been found guilty of racial harassment after describing an Asian political opponent as "a coconut" during a heated debate today.

Shirley Brown, 48, the first black Liberal Democrat elected to Bristol city council, who employed the term about a Conservative, Jay Jethwa, denied committing an offence.

Bristol magistrates court heard the term was used to accuse someone of betraying their heritage by pandering to white opinion, just as a coconut was brown on the outside but white in the middle.

She was given a 12-month conditional discharge and ordered to pay £620 in costs. The chairman of the bench, Simon Cooper, told her the remark had been "purely gratuitous" and could have stimulated racial hatred.

"You made a mistake for which you have to accept responsibility," he added. "It is a sad case."

Brown's remark came as she argued against a Conservative attempt in February 2009 to cut funds to the council's Legacy Commission, established in 2008, the year after the bicentenary of the abolition of the slave trade in the British empire.

Jethwa had said spending £750,000 of taxpayers' money "righting the wrongs of slavery" did not make sense. Ian Jackson, prosecuting, said Brown "was heard to say: 'In our culture we have a word for you which many in this city would understand, a coconut.

"And at the end of the day I just look at you as that. And the water's either worth throwing away or drinking it'."

Jethwa, 42, did not hear the remark during the council meeting but watched it later on a webcast.

She wept as she told the court: "I was completely shocked and I was numb and had to rewind the footage to see if it was only me she had directed the comment to. I was very, very upset and distressed.

The word is doubly insulting as it insults both me and the white population."

She considered Brown's remarks about the water as "racist" and "to mean that my comments were worth throwing out.

The Conservative party lodged a formal complaint and a member of the public then complained to Avon and Somerset police, who launched a criminal investigation.

Brown was suspended for a month by the council's standards committee last summer for using "offensive and abusive language", although it did not judge the remarks racist.